The present application relates to a receiving apparatus and a receiving method for use therewith, the receiving apparatus being used by diverse video equipment such as Television (TV) sets for receiving broadcast waves including those of digital TV broadcasts.
In recent years in Japan, in the United States, in Europe and elsewhere, efforts have been underway to promote TV broadcast digitization in order to offer high-definition and multi-channel TV programs, multimedia services, and stable reception of TV signals by mobile units. FIG. 4 shows a typical structure of an existing receiving apparatus incorporated in TV sets and recording devices for receiving digital TV broadcasts. In the receiving apparatus shown in FIG. 4, a broadcast signal received by an antenna 11 is fed to a filter 12. The filter 12 is a band-pass filter (BPF) that extracts frequency bands of the broadcast signal. A received signal extracted by the filter 12 is forwarded to a variable amplification section 13. The amplification factor of the variable amplification section 13 is controlled by a command “a” based on the result of detection performed by a distortion detection section 19, to be described later.
The received signal amplified by the variable amplification section 13 is sent to a mixing section 15 through a filter 14. The filter 14 is another band-pass filter that extracts frequency bands of the broadcast signal. The mixing section 15 mixes the received signal coming from the filter 14 with a frequency signal supplied by a channel selection frequency signal generation section 16, thereby turning the received signal of a given frequency into an intermediate frequency signal. The frequency of the signal output by the channel selection frequency signal generation section 16 varies with reception frequency (i.e., received channel).
The intermediate frequency signal acquired by the mixing section 15 is forwarded to a variable amplification section 18 through a filter 17. The filter 17 is a band-pass filter that allows only the frequency band of the intermediate frequency signal to pass through. The intermediate frequency signal amplified by the variable amplification section 18 is fed to a demodulation section 20 for demodulation whereby a digital TV broadcast signal is obtained. The digital TV broadcast signal appears at an output terminal 21. The amplification factor of the variable amplification section 18 is controlled by a command “b” coming from the demodulation section 20. The amplification factor is controlled in such a manner as to keep within a predetermined range the level of the intermediate frequency signal being input to the demodulation section 20.
The intermediate frequency signal output by the mixing section 15 is fed to the distortion detection section 19. The distortion detection section 19 detects the signal level of the received intermediate frequency signal and compares the detected signal level with a predetermined target level. If the detected signal level is found deviating from the target level, a suitable command is sent to the variable amplification section 13 to vary its amplification factor in a manner bringing the signal level of the intermediate frequency signal to the target level through what is known as an automatic level control (AGC) circuit.
One such receiving apparatus for receiving TV broadcast signals is disclosed illustratively in Japanese Patent Laid-open No. 2007-116358.